Partenaires et organisations internationales
(Anglais)
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Riso (DK), IRD (DK), Rolls Royce (UK), Gaz de France (F), Institut National Polytechnique Grenoble (F), Napier University Ventures (UK)
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Résumé des résultats (Abstract)
(Anglais)
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Solid oxide fuel cells (SOFC) are all-ceramic, electrochemical devices that convert chemical energy of a fuel (hydrogen, hydrocarbons) into electricity with potentially very high efficiency (50-60%) and recoverable heat at a high quality temperature level (700-1000°C), using ambient air as oxidant. The elements are made from a dense ceramic electrolyte membranes (Y2O3-ZrO2, YSZ, conductors for O2- ions), sandwiched between porous electrodes (based on Ni as anode and electronically conducting LaSrMnO3, LSM, as ceramic cathode). These trilayers are stacked with interconnecting bipolar plates to give modules of kWel size or more. SOFC have enormous potential on the future electricity market.
An important limitation is cost per power density. The aim of this project was to fabricate low-cost SOFC stack components, yielding high power density, by using cheap state-of-the-art materials and cheap, environmental-friendly techniques.
Specific objectives were (1) the development of inks and printing or casting techniques for (1a) thin (< 40 mm) YSZ electrolytes (3Y, 8Y), for (1b) cathodes with a gradient structure made of LSM-YSZ and LaSrCoO3-LSM composites, and for (1c) anodes with a gradient structure made of Ni-YSZ cermets or doped LaCrO3. Furthermore to (2) fabricate dense and stable interconnecting plates out of LaCrO3, (3) to test and optimize the performance at 750-900°C with hydrogen and methane fuels, of single cells and short stacks, finally to (4) assess cost and environmental aspects of the full fabrication process.
Two designs were pursued : (i) printing of thin anode, electrolyte, cathode and interconnect layers on hollow porous support plates, and (ii) printing or casting of thin electrolyte and cathode on porous support anodes, using interconnect plates for stacking. Targets were set to achieve power densities of 0.5 W/cm2 at 800°C and 0.8 W/cm2 at 900°C.
The consortium consisted of a large manufacturer of power stations, a large end-user utility, two manufacturings SMEs and three leading research institutes. EPFL's contribution focussed on two major tasks : 1) the only partner to use an innovative tape casting technique (instead of screen printing), on water-basis, to fabricate both the anode supports and ultrathin electrolytes (5 mm), in a single step. The only cost factor in this process is a high temperature (1350°C) heating cycle in a furnace. 2) fabrication of ceramic anode materials (chromite- and ceria-based) for operation with hydrocarbon-rich fuel. Additional tasks were assisting in the cost and environmental assessment of the fabrication, and electrochemical cell testing. EPFL was task leader for the Anode.
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